Livestock Update, September 2000
Scott Greiner, Extension Animal Scientist, Beef, Virginia Tech
Virginia BCIA to Sponsor Consignment Bull and Heifer Sales
The Virginia Beef Cattle Improvement Association will sponsor two all-breed performance tested bull and commercial heifer sales in fall 2000. A November 17 sale is scheduled at the Southside Livestock Market in Blackstone, Va., and the second sale will be held December 2 at Augusta Expoland near Staunton, Va.
Bulls born September 1, 1998, to October 31, 1999, will be eligible for the sales. Bulls must have been performance tested, and have complete weaning and yearling records available. To be eligible for sale, Angus and Hereford bulls need to have breed average or better YW EPDs, while Charolais, Gelbvieh, and Simmental bulls need to have YW EPDs above the 70th percentile for their respective breed.
The sale at Blackstone will offer both bred and open heifers, while at Staunton only bred heifers will be offered. Bred heifers (born September 1, 1998, to April 30, 1999) will be confirmed pregnant to calve January 1 to April 15, 2001. Heifers will be bred to calving-ease bulls, with EPDs documented. Breed composition and pedigree information on heifers will be made available. Open heifers to sell at Blackstone will be born March 1 to October 31, 1999.
Breeders in Virginia and bordering states who are members of Virginia BCIA are eligible to consign bulls (only Virginia breeders may consign heifers). The sales will be managed by VA Sale Services in Staunton, Va. For copies of the rules and regulations as well as entry information, contact the Virginia BCIA office at (540) 231-9163. Consignment deadline is October 1.
Virginia BCIA Adopts EPD Requirements for Central Bull Tests and Consignment Sales
The Virginia Beef Cattle Improvement Association has adopted minimum EPD requirements for the 2000-01 Central Bull Test Sales at Culpeper and Wytheville, as well as the 2000 consignment sales held in Blackstone and Staunton. To be eligible for sale, bulls must meet minimum Yearling Weight Expected Progeny Difference (EPD) requirements. These requirements are the same as those utilized in the Virginia Quality Assured feeder calf tagging program operated by the Virginia Cattlemen's Association.
Minimum EPDs for the 2000-01 test year will be based on non-parent EPD summaries published by breed associations in the spring of 2000. In the case in which a YW EPD does not exist, WW EPD will be used to determine eligibility. The YW EPD requirements are as follows for the various breeds:
|Minimum EPD Requirements|
Minimum YW EPD
|Minimum WW EPD|
(only used in the absence of YW EPD)
Understanding EPDs: Part 1
Note: This article is Part 1 in a three part series dealing with EPDs.
Expected progeny differences (EPDs) are an estimate of the genetic value of an animal as a parent. Specifically, EPDs predict the difference in performance of the future offspring of a parent, compared to the future offspring from another parent in the same breed (when each is mated to animals of the same genetic merit). EPDs are calculated for birth, growth, maternal, and carcass traits and are reported in the units of measurement for a specific trait (normally pounds). EPD values may only be directly compared between animals within a particular breed. In other words, a birth weight EPD for a Charolais bull may not be directly compared to a birth weight EPD of a Hereford bull (unless adjustments are made to account for breed differences- Across Breed EPDs).
EPDs are reported by most major beef breed associations, and are calculated using complex statistical equations and models. These statistical models use all known information that exists on a particular animal for calculation of its EPD. This information includes performance data (i.e. weight records) on the animal itself, information from its ancestors (sire and dam, grandsire, great grandsire, maternal grandsire, etc.), collateral relatives (brothers and sisters), and progeny (including progeny that are parents themselves as well as grandprogeny). In short, virtually all performance data that relates to the animal of interest is used to calculate its EPD. These performance records are adjusted for such factors as age, sex, and age of dam prior to inclusion in EPD databases. These adjustment factors allow performance records to be fairly compared when used in the analysis. Additionally, genetic merit of mates is accounted for with the use of progeny information. Therefore, progeny records are not influenced by superior or inferior mates. The statistical analysis used for EPD calculation also removes the effects of environment (nutrition, climate, geographical location, etc.) that exist between herds. These environmental effects can be removed due to the widespread use of artificial insemination. Through AI, the same bull can be used in several herds across the country. These common sires create genetic links between herds with differing environments. These genetic links serve as the foundation for evaluation of performance data and EPD calculation across herds. For these reasons, animals with published EPDs within a breed may be directly compared regardless of their age and origin. Finally, the relationships that exist between various traits are considered in the calculations.
Birth Weight EPDs:
EPDs are most useful to directly compare individuals for a trait of interest. In the above example, assume that the two bulls were each mated to the same set of cows. The difference in the birth weight EPD value between Bull A and Bull B is 4 pounds (5 - 1 = 4). Therefore, Bull A would be expected to sire calves that are 4 pounds heavier at birth on the average than calves sired by Bull B. It is important to recognize that EPDs predict the expected difference in performance, not the actual performance. In other words, the EPDs for Bulls A and B suggest there will be 4 pounds difference in birth weight in their progeny when we mate them comparably. EPDs do not predict what the actual birth weight of the calves will be.
Research has documented that most calving difficulty is caused heavy calves at birth. Birth weight EPDs are the most accurate indicators of genetic differences for birth weight. Therefore, considerable emphasis should be placed on birth weight EPDs when selecting bulls for use on heifers.
Calving Ease EPD:
Some breed associations publish calving ease EPDs (Gelbvieh and Simmental most notably). This EPD predicts the ease with which a bull's calves are born to first-calf heifers. Calving ease EPDs are reported as deviations in percentage of unassisted births. In the above example, if Bulls A and B were bred to the same set of heifers, we would expect the heifers bred to Bull B to have a 5% advantage in unassisted births. In other words, we wold expect less calving problems when Bull B was bred to heifers. These calving ease EPDs may also be reported in a ratio form. For example, if Bull A had a calving ease EPD of 100 and Bull B 105 we would draw the same conclusions: heifers bred to Bull B would have a 5% advantage in unassisted births.
Calving ease EPDs should be used in concert with birth weight EPDs as another tool to use for avoiding dystocia problems in the cowherd. The front of breed sire summaries should be consulted to interpret the meaning of calving ease EPDs for each breed.
Weaning and Yearling Weight EPDs:
Weaning and yearling weight EPDs are indicators of the growth genes that will be passed from an animal to their progeny. Weaning weight EPDs predict the average difference in weaning weight of a bull's progeny compared to progeny of another bull. This weaning weight difference is predicted for a standard weaning age of 205 days. In the above example, we would expect calves sired by Bull A to weigh 10 pounds more at weaning than calves sired by Bull B. This difference in weaning weight is attributed solely to differences in genes for growth passed from the bulls to their offspring. The milking ability of the cow is not considered in this EPD. Rapid early growth is an important selection criteria for cow-calf producers since feeder cattle are sold by the pound. Therefore, emphasis should be placed on weaning weight EPDs when considering bulls.
Yearling weight EPDs predict the average difference in weight of a bull's progeny at a year of age (365 days). Using the EPDs for Bulls A and B above, we would expect calves sired by Bull A to be 20 pounds heavier at a year of age on the average than calves sired by Bull B. Yearling weight EPDs are the most useful indicators of growth rate of slaughter progeny in the feedlot.
Maternal Milk EPDs:
Milk EPDs are expressed slightly differently than birth and growth EPDs. Milk EPDs reflect the milking ability of an animal's daughters. This difference in milking ability is expressed as additional pounds of calf weaned by a bull's daughters. Considering the milk EPDs for Bulls A and B, we would expect daughters of Bull A to wean calves that are 5 pounds heavier at weaning than calves out of daughters of Bull B. This difference is due to the superior milk production of daughters sired by Bull A. Milk EPDs are reflected in weaning weight of a bull's grandprogeny (calves by his daughters).
Milk EPDs are important in bull selection when replacements will be retained in the herd. Optimum milk EPDs need to be determined that match the feed resources and environment of the operation. In other words, more milk is not necessarily better as heavier milking cows may require more nutritional inputs to maintain body condition and reproductive efficiency. Breed needs to be an important consideration when evaluating milk EPDs. Very high milk EPDs for bulls in breeds noted for heavy milking ability may not be advantageous.
Visit Virginia Cooperative Extension